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J Biol Chem. 2019 Sep 20;294(38):14068-14080. doi: 10.1074/jbc.RA118.006583. Epub 2019 Jul 31.

Acute ethanol exposure reduces serotonin receptor 1A internalization by increasing ubiquitination and degradation of β-arrestin2.

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Department of Physiology and Pharmacology, Wake Forest School of Medicine, Winston Salem, North Carolina 27157.
Center for Molecular Signaling, Department of Biology, Wake Forest University, Winston Salem, North Carolina 27106.
Department of Physiology and Pharmacology, Wake Forest School of Medicine, Winston Salem, North Carolina 27157
Center for the Neurobiology of Addiction Treatment, Wake Forest School of Medicine, Winston Salem, North Carolina 27157.


Acute alcohol exposure alters the trafficking and function of many G-protein-coupled receptors (GPCRs) that are associated with aberrant behavioral responses to alcohol. However, the molecular mechanisms underlying alcohol-induced changes in GPCR function remain unclear. β-Arrestin is a key player involved in the regulation of GPCR internalization and thus controls the magnitude and duration of GPCR signaling. Although β-arrestin levels are influenced by various drugs of abuse, the effect of alcohol exposure on β-arrestin expression and β-arrestin-mediated GPCR trafficking is poorly understood. Here, we found that acute ethanol exposure increases β-arrestin2 degradation via its increased ubiquitination in neuroblastoma-2a (N2A) cells and rat prefrontal cortex (PFC). β-Arrestin2 ubiquitination was likely mediated by the E3 ligase MDM2 homolog (MDM2), indicated by an increased coupling between β-arrestin2 and MDM2 in response to acute ethanol exposure in both N2A cells and rat PFC homogenates. Importantly, ethanol-induced β-arrestin2 reduction was reversed by siRNA-mediated MDM2 knockdown or proteasome inhibition in N2A cells, suggesting β-arrestin2 degradation is mediated by MDM2 through the proteasomal pathway. Using serotonin 5-HT1A receptors (5-HT1ARs) as a model receptor system, we found that ethanol dose-dependently inhibits 5-HT1AR internalization and that MDM2 knockdown reverses this effect. Moreover, ethanol both reduced β-arrestin2 levels and delayed agonist-induced β-arrestin2 recruitment to the membrane. We conclude that β-arrestin2 dysregulation by ethanol impairs 5-HT1AR trafficking. Our findings reveal a critical molecular mechanism underlying ethanol-induced alterations in GPCR internalization and implicate β-arrestin as a potential player mediating behavioral responses to acute alcohol exposure.


E3 ubiquitin ligase; G-protein– receptor (GPCR); alcohol; arrestin; mouse double minute2 homolog (MDM2); proteasome; protein degradation; receptor trafficking; serotonin 5-HT1A receptor; ubiquitylation (ubiquitination)

[Available on 2020-09-20]

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